Compact wide field of view digital camera with stray light impact suppression
A point action camera or other compact digital camera having a wide field of view, includes an optical assembly that includes multiple lens elements, including at least one lens element that has an aspheric lens surface. The optical assembly is configured to provide a field of view in excess of 120 degrees. The digital camera is configured such that not less than 90% of return ghosts foci are more than +/−2 mm from the image sensor plane.
1. A digital point action camera, comprising
an optical assembly for a point action camera having a wide field of view, comprising multiple lens elements, including one or more aspheric lens surfaces, configured to provide a field of view in excess of 120 degrees; and
an image sensor disposed approximately at a focal plane of the optical assembly; and
a digital camera housing including electronics and a user interface, and containing said optical assembly and said image sensor in optically effective relative disposition; and
wherein the optical assembly comprises, from object end to image end:
a first optical group including two lens elements configured to collect and reduce a field angle of light incident at said wide field of view;
a second optical group, including three lens elements; and
a third optical group including two doublets and a singlet disposed between the two doublets, and
an aperture stop between said second and third optical groups, and
wherein said singlet of said third optical group includes an aspheric surface that is configured to compensate higher order astigmatism, and
wherein said digital camera comprises a MTF at 200 lp/mm above 0.35 and a MTF at 100 lp/mm above 0.55.
2. The digital camera of claim 1 , wherein a ratio of a diameter of a first lens element at the object end of the optical assembly to an image diagonal is less than approximately 3.
3. The digital camera of claim 1 , wherein a diameter of a first lens element at the object end of the optical assembly; is less than 30 mm.
4. The digital camera of claim 1 , comprising less than five microns of lateral chromatic aberration.
5. The digital camera of claim 1 , comprising a ratio of total track length, from the object end of the optical assembly to the focal plane, to effective focal length of the optical assembly (hereinafter “TTL/EFL”) that is less than 12.
6. The digital camera of claim 1 , wherein a total track length TTL, from the object end of the optical assembly to the focal plane, is less than 10 cm.
7. The digital camera of claim 1 , wherein the second group comprises a positive focal length in a range between 10 mm and 25 mm.
8. The digital camera of claim 1 , wherein the second optical group is spaced apart from the first optical group by approximately 27.5 mm.
9. The digital camera of claim 8 , wherein said first optical group comprises a convexo-concave or meniscus lens.
10. The digital camera of claim 8 , wherein said second optical group is spaced apart from the third optical group by approximately 12.1 mm.
11. The digital camera of claim 8 , wherein the first optical group comprises a negative focal length in a range between −5 mm and −20 mm.
12. The digital camera of claim 8 , wherein the third optical group further comprises a positive focal length of approximately 41.878 mm.
13. The digital camera of claim 1 , wherein at least one aspheric surface comprises an aspheric sag less than approximately 12 microns.
14. The digital camera of claim 1 , wherein at least one aspheric surface comprises an aspheric sag slope less than approximately 15 microns per millimeter.
15. The digital camera of claim 1 , comprising a single aspheric lens element, which is the only aspheric lens element within the optical assembly, wherein lens elements other than the single aspheric lens element comprise spherical or planar lens surfaces, or both, each without significant aspheric departure.
16. The digital camera of claim 1 , comprising a single aspheric lens surface, which is the only aspheric lens surface within the optical assembly, wherein lens surfaces other than said aspheric lens surface comprise spherical or planar lens surfaces, or both, each without significant aspheric departure.
17. The digital camera of claim 1 , comprising only one aspheric lens element.
18. The digital camera of claim 1 , comprising only one aspheric lens surface.
19. The digital camera of claim 1 , wherein a stray light irradiance ratio is below 1/10,000.
20. The digital camera of claim 1 , wherein a stray light power ratio is below 1/100.
21. The digital camera of claim 1 , wherein axial chromatic aberration is less than 0.025 microns.
22. The digital camera of claim 21 , wherein the axial chromatic aberration is defined by a ray trace at 0.7 zonal in the stop, and across a spectral band between 465 nm to 650 nm.